JP2008301241A - Loop antenna and radio transmitter/receiver with loop antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a loop antenna capable of reducing communication disabled areas. <P>SOLUTION: The loop antenna is used for the radio transmitter/receiver which performs communication with a radio communication medium by non-contact by electromagnetic wave, wherein a loop antenna for transmission which transmits information by a carrier, a first self-resonance loop coil arranged inside on the same plane of the loop antenna for transmission, a loop antenna for reception arranged inside on the same plane of the first self-resonance loop coil, a second self-resonance loop coil arranged inside on the same plane of the loop antenna for reception, and a third self-resonance loop coil arranged inside on the same plane of the second self-resonance loop coil, are arranged. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a loop antenna used for a wireless transmission / reception apparatus that performs non-contact communication with an IC card used as a commuter pass in an automatic ticket gate system, and a wireless transmission / reception apparatus including the loop antenna.

  At present, information is magnetically recorded in commuter passes used in, for example, automatic ticket gate systems. When a commuter pass is inserted in an automatic ticket checker, magnetic information is recorded in the portion where the magnetic record is made. Information is read by contacting the head.

  For this reason, when the commuter pass is stored in the case, the user needs to take it out and insert it into the automatic ticket gate, which is troublesome.

Therefore, a contactless card system was developed. According to this contactless card system, it is possible to exchange information (data communication) and the like in a contactless manner, and this is applied to the automatic ticket gate system as described above. It is now possible to enter and exit the automatic ticket gate even when stored. (For example, refer to Patent Document 1.)
JP-A-8-194785 (Third Mitigation, FIG. 13)

  In recent years, IC cards have become widespread, and there are many cases where one user has several IC cards, and there are also users who carry a plurality of IC cards in a single card compartment.

  If the user uses two IC cards stacked, the amplitude of the return signal from the IC card received by the wireless transmission / reception device becomes extremely small as compared with the case of only one IC card. The phenomenon that the received signal cannot be demodulated normally occurs. In other words, even if only one IC card can be used, there is a problem that communication performance is poor when two cards are used in an overlapping manner, resulting in poor system performance.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a loop antenna capable of reducing a communication incompetent region and a wireless transmission / reception apparatus including the loop antenna.

In order to achieve the above object, a loop antenna according to the present invention is a loop antenna used in a wireless transmission / reception apparatus that performs non-contact communication with a wireless communication medium using electromagnetic waves, and is used for transmitting information by a carrier. A loop antenna, a first self-resonant loop coil disposed on the same plane of the transmission loop antenna, and a reception loop antenna disposed on the same plane of the first self-resonant loop coil A second self-resonant loop coil disposed inside the same plane of the reception loop antenna, and one or more second self-resonant loop coils disposed inside the same plane of the second self-resonant loop coil. 3 self-resonant loop coils.

In order to achieve the above object, a wireless transmission / reception apparatus including a loop antenna according to the present invention is a wireless transmission / reception apparatus that performs non-contact communication with a wireless communication medium using electromagnetic waves, and transmits information using a carrier. A transmission loop antenna;
A first self-resonant loop coil disposed inside the same plane of the transmitting loop antenna; a receiving loop antenna disposed within the same plane of the first self-resonant loop coil; and the reception A second self-resonant loop coil arranged inside the same plane of the loop antenna for use, and one or a plurality of third self-resonances arranged inside the same plane of the second self-resonant loop coil A loop coil, a transmission circuit connected to the transmission loop antenna for outputting an electrical signal for wireless transmission, and an electric wave from an electromagnetic wave received by the reception loop antenna connected to the reception loop antenna It has a receiving circuit which receives a signal, and a central processing unit which controls the transmitting circuit and the receiving circuit.

An object of the present invention is to reduce an incommunicable region caused by stacking a plurality of IC cards.

Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a configuration example of a contactless card system. This non-contact card system supplies, for example, an IC card 11 corresponding to the above-mentioned commuter pass and power to be used as a non-contact power source to the IC card using electromagnetic waves as a medium, as well as reading and writing data and others And a wireless transmission / reception device 12 that performs necessary processing.

  FIG. 2 shows a configuration example of the wireless transmission / reception device 12. In the wireless transmission / reception device 12, data is radiated as an electromagnetic wave from the loop antenna 1000 whose coil has a rectangular cross-sectional shape in accordance with a command and necessary write information.

  That is, first, a transmission circuit 2 is controlled in a CPU (abbreviation of Central Processing Unit, hereinafter referred to as CPU) 1 so as to apply a voltage corresponding to a predetermined modulation wave to the loop antenna 1000 according to a predetermined program.

  A transmission circuit 2 that outputs an electrical signal for performing wireless transmission receives a carrier from a carrier generator 21 that generates a carrier having a predetermined frequency (for example, a frequency of an ultrashort wave band or lower), and the carrier from the carrier generator 21. In recording and transmitting information, a modulation circuit 22 that converts the signal into an optimal electrical signal according to the information and the nature of the recording / transmission medium, a carrier is received from the modulation circuit 22, and the amplification factor changes under the control of the CPU 1 The amplifier circuit 23 includes a matching circuit 24 that matches the output impedance of the amplifier circuit 23 on the carrier sending side received from the amplifier circuit 23 with the input impedance of the loop antenna 1000 on the receiving side.

  The amplification factor of the amplifier circuit 23 is controlled by the CPU 1 in accordance with a command to be transmitted to the IC card, write data, or the like. Therefore, in the amplification circuit 23 via the modulation circuit 22, the carrier outputs an amplitude-modulated wave according to a command or write data to be transmitted to the IC card. The output terminal of the amplifier circuit 23 is connected to the loop antenna 1000 via the matching circuit 24. Therefore, the amplitude-modulated wave output from the amplifier circuit 23 via the modulation circuit 22 is supplied to the loop antenna 1000. . That is, a voltage corresponding to the amplitude-modulated wave is applied to the loop antenna 1000. Thereby, in the loop antenna 1000, a current corresponding to the voltage flows, and a magnetic field (magnetic flux) corresponding to the change in the current is generated.

  That is, from the loop antenna 1000, the amplitude-modulated wave output from the amplifier circuit 23 via the modulation circuit 22 is radiated as an electromagnetic wave.

  Thereafter, in the wireless transmission / reception device 12, the CPU 1 controls the amplification factor of the amplifier circuit 23 so as to be a constant value, whereby an unmodulated wave is radiated as an electromagnetic wave in the same manner as the amplitude-modulated wave described above. Then, it is determined whether or not there is a response from the IC card 11.

  When the CPU 1 determines that there is no response from the IC card 11, that is, the distance between the IC card and the wireless transmission / reception device 12 that causes mutual induction between the loop antenna of the IC card 11 (not shown) and the loop antenna 1000. If not, the process of radiating the amplitude modulated wave and the unmodulated wave is repeated as described above until there is a response from the IC card 11.

  Next, the loop antenna 1000 of the wireless transmission / reception apparatus 12 of the present invention will be described.

  As shown in FIG. 3, the loop antenna 1000 of the present invention is composed of, for example, seven loop coils.

  The transmission loop antenna 200 is connected to the transmission circuit 2 and radiates the carrier frequency transmitted from the transmission circuit 2 to an IC card (not shown). The transmission loop antenna 200 is composed of a single printed board wiring, and the transmission loop antenna 200 surrounds all the antennas. The loop shape of the transmission loop antenna 200 is wound in a rectangular shape. The transmission loop antenna 200 includes a transmission loop antenna capacitor 201 connected in parallel to form a resonance circuit.

  The first self-resonant loop coil 400 is disposed inside the transmission loop antenna 200 and is limited by the transmission circuit 2 by receiving the magnetic field radiated from the transmission loop antenna 200 and further radiating the magnetic field by mutual induction. It becomes possible to radiate the magnetic field more strongly while keeping the power supply output constant.

  The first self-resonant loop coil 400 is composed of two turns of printed circuit board wiring, and a first self-resonant loop coil capacitor 401 is connected in series. The resonance frequency is set to a frequency different from the resonance frequency of the transmission loop antenna 200 described above (a high value in units of several MHz). Since the first self-resonant loop coil 400 is set to a resonance frequency different from that of the transmission loop antenna 200, the first self-resonance loop coil 400 is hardly influenced by the resonance frequency of each other's antenna. Further, the shape of the coil loop of the first self-resonant loop coil 400 is a rectangle.

  A reception loop antenna 300 is disposed inside the first self-resonant loop coil 400.

  The reception loop antenna 300 is composed of one turn of printed wiring. The reception loop antenna 300 is connected to the reception circuit 3, receives information from the IC card, and outputs the information to the reception circuit 3. Further, a reception loop antenna capacitor 301 is connected in parallel to form a resonance circuit.

  By setting the resonance frequency of the reception loop antenna 300 to a frequency shifted in the high direction in units of several MHz with respect to the carrier frequency, it is possible to obtain reception characteristics with little influence from the phase of the carrier frequency. is there.

  The second self-resonant loop coil 500 is disposed inside the reception loop antenna 300. The second self-resonant loop coil 500 receives the magnetic field radiated from the transmission loop antenna 200 and radiates the magnetic field further by mutual induction, thereby generating a magnetic field while keeping the power output limited by the transmission circuit 2 constant. It becomes possible to radiate more strongly.

  The second self-resonant loop coil 500 is composed of one turn of printed board wiring, and a second self-resonant loop coil capacitor 501 is connected in series. The resonance frequency is set to a frequency different from the resonance frequency of the reception loop antenna 300 (a low value in units of several MHz). The shape of the coil loop of the second self-resonant loop coil 500 is a rectangle.

  In addition, since the second self-resonant loop coil 500 is set to a resonance frequency different from that of the reception loop antenna 300 and other nearby loop coils, the second self-resonance loop coil 500 is hardly influenced by the resonance frequency of each other antenna. .

  The three third self-resonant loop coils 600 are each composed of six turns of printed board wiring inside the second self-resonant loop coil 500.

  A third self-resonant loop coil capacitor 601 is connected in series to the three third self-resonant loop coils 600. Since the resonant frequency is set to a frequency different from the resonant frequency of the second self-resonant loop coil 500, the resonant frequency is hardly affected by the resonant frequency of the antennas.

  The three third self-resonant loop coils 600 further receive the magnetic fields radiated by the receiving loop antenna 300 and the second self-resonant loop coil 500 to radiate magnetic fields by mutual induction, further increasing the communicable distance with the IC card. It becomes possible to improve.

The winding directions of the three third self-resonant loop coils 600 are wound in the same direction as the transmitting loop antenna 200, the first self-resonant loop coil 400, and the second self-resonant loop coil 500. More than the first self-resonant loop coil 400 is effective.

  In addition, the number of the third self-resonant loop coils 600 is effective even when the number of the third self-resonant loop coils 600 is one to four or more (FIG. 4 shows the case where the number of the third self-resonant loop coils 600 is two, and FIG. The number of self-resonant loop coils 600 is four.) However, the null region is minimized because the number of third self-resonant loop coils 600 is three. Is the case.

  All antennas and coils are wound in the same direction.

  Further, the capacitances of the capacitors used in the antenna and the self-resonant loop coil of this embodiment are in the order of 201> 501> 401 = 601> 301.

  All antennas and coils are configured within a range in which mutual induction effects are exerted.

  All antennas and self-resonant loop coils are formed on the same substrate.

  By performing this embodiment, it is possible to improve the communication performance for a plurality of IC cards stacked. In this embodiment, the communication characteristics for one IC card can be secured.

The number of turns of the first self-resonant loop coil is effective regardless of the number of turns, but it is optimal to use two turns.

The shape of the loop antenna 1000 is optimal for obtaining a maximum communicable area within a prescribed substrate size, but it is effective not only for a rectangle but also for a substantially rectangle or an ellipse.

The three third self-resonant loop coils 600 do not necessarily have the same size. The number of turns of the self-resonant loop coil 600 may not be the same.

The figure which shows the structural example of the non-contact card system by this invention. The block diagram which shows the structural example of the radio | wireless transmitter / receiver 12 by this invention. The figure which shows the 1st Example which shows the loop antenna 1000 with which the radio | wireless transmitter / receiver 12 by this invention was equipped. The top view of the Example of the loop antenna 1000 which provided the 3rd self-resonance loop coil 600 with which the radio | wireless transmitter / receiver 12 by this invention was equipped. The top view of the Example of the loop antenna 1000 which provided the 3rd self-resonance loop coil 600 with which the radio | wireless transmitter / receiver 12 by this invention was equipped.

Explanation of symbols

1 CPU
2 transmitting circuit 3 receiving circuit 200 transmitting loop antenna 300 receiving loop antenna 400 first self-resonant loop coil 500 second self-resonant loop coil 600 third self-resonant loop coil

Claims (2)

A loop antenna used in a wireless transmission / reception device that performs non-contact communication with a wireless communication medium by electromagnetic waves,
A transmission loop antenna for transmitting information by a carrier;
A first self-resonant loop coil disposed inside the same plane of the transmitting loop antenna;
A receiving loop antenna disposed on the inner side of the first self-resonant loop coil on the same plane;
A second self-resonant loop coil disposed inside the same plane of the receiving loop antenna;
A third self-resonant loop coil disposed within the same plane of the second self-resonant loop coil;
A loop antenna characterized by comprising: A wireless transmission / reception device that performs non-contact communication with a wireless communication medium by electromagnetic waves,
A transmission loop antenna for transmitting information by a carrier;
A first self-resonant loop coil disposed inside the same plane of the transmitting loop antenna;
A receiving loop antenna disposed on the inner side of the first self-resonant loop coil on the same plane;
A second self-resonant loop coil disposed inside the same plane of the receiving loop antenna;
A third self-resonant loop coil disposed within the same plane of the second self-resonant loop coil;
A transmission circuit connected to the transmission loop antenna for outputting an electric signal for wireless transmission;
A receiving circuit connected to the receiving loop antenna and receiving an electric signal from an electromagnetic wave received by the receiving loop antenna;
A central processing unit for controlling the transmitting circuit and the receiving circuit;
A wireless transmission / reception device comprising:

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